Help in calculating interest rate.

Hi to all, I have been reading this site and hope that someone will be able to help with some figures and calculations that I have.

I have been trying to find the answer for a very long time and really hope that there are some wizards who can crack the answer.

I want to know if the interest rate has been calculated correctly please.

I have a loan of £37,672.00 for 303 months.

The first 3 months I don't have to pay anything.

Then I have to pay £285.79 for 12 months at an interest rate of 7.80%

Then I have to pay £335.79 for 288 months at an interest rate of 9.80%

I have tried doing this myself by £37,672.00 x 7.80% and 9.80% but admit that I am hopeless at getting the figures to match.

Any help or advice will be very much appreciated and thank you in advance